Lens type functional retroreflective sheeting and method of producing same

ABSTRACT

This invention relates to lens type functional retroreflective sheeting having retroreflective regions and visual functionality presenting regions, the retroreflective sheeting comprising: 
     a base sheet consisting of a support comprising a functional resin layer containing a functional pigment having light-storing or fluorescent properties, microspherical lens-embedding regions in which microspherical lenses are densely distributed on the surface of the functional resin layer of the support so as to form a mono-layer, and microspherical lens-free regions in which substantially no microspherical lens is embedded and the functional resin layer is exposed; 
     a transparent protective film disposed above the microspherical lens-bearing surface of the base sheet; and 
     bonds at which said base sheet and said transparent protective film are partly bonded together. This lens type functional retroreflective sheeting not only afford good visibility to viewers positioned in the direction of the light source (e.g., automobile drivers), but also afford good visibility at night to drivers and pedestrians positioned in directions different from the that of the light source.

TECHNICAL FIELD

This invention relates to lens type functional retroreflective sheetingwhich is useful in signs such as road signs, guide signs andconstruction signs, license plates for vehicles such as automobiles andmotorcycles, safety goods such as safety clothing, safety shoes andlife-saving devices, signboards, markings for vehicles, and the like.

More particularly, it relates to lens type functional retroreflectivesheeting having retroreflective regions and visual functionalitypresenting regions, the retroreflective sheeting comprising:

a base sheet consisting of a support comprising, as an essentialcomponent, a functional resin layer containing a functional pigmenthaving light-storing or fluorescent properties, microsphericallens-embedding regions in which microspherical lenses are denselydistributed on the surface of the functional resin layer of the supportso as to form a mono-layer, and microspherical lens-free regions inwhich essentially no microspherical lens is embedded and the functionalresin layer is exposed;

a transparent protective film disposed above the microsphericallens-bearing surface of the base sheet; and

bonds at which said base sheet and said transparent protective film arepartly bonded together.

BACKGROUND ART

Conventionally, retroreflective sheeting capable of reflecting incidentlight back toward the light source has been well known, and suchsheeting is widely used in the above-described fields of applicationowing to good visibility at night on the basis of its retroreflectivity.For example, road signs, construction signs and other signs usingretroreflective sheeting have excellent characteristics in that, atnight or the like, they reflect light from a light source (e.g., theheadlamps of a moving vehicle such as automobile) back toward the lightsource (i.e., the moving vehicle) and afford good visibility to theviewer of the signs (i.e., the driver of the vehicle), thus permittingthe transmission of correct information.

Thus, retroreflective sheeting generally reflects light from a lightsource back toward the light source and hence affords good visibility inthe direction of the light source. However, when the viewer ispositioned in a direction different from that of the light source, itsvisibility is markedly reduced. Moreover, owing to the nature ofretroreflective sheeting, the difference between the angle of incidenceof light from the light source of a vehicle such as an automobile andthe angle of observation of the driver of the vehicle increases as thelight source comes nearer, resulting in a marked reduction invisibility. Recently, with the development of road systems and thediversification of provided information, the amount of informationdisplayed on each sign is increasing. With consideration for the speedof vehicles, it may be very difficult for the drivers to read necessaryinformation in a very short period of time when they are within thevisible range of retroreflected light.

Accordingly; in the case of applications requiring the provision of morecorrect information, pronounced propaganda effects and the like,conventional retroreflective sheeting having retroreflectivity alone islimited in visibility. In particular, there is a strong demand forexcellent retroreflective sheeting which can always afford goodvisibility to viewers at night even when the viewers are positioned indirections different from that of the light source.

In order to meet this demand, various attempts have been made to improvethe visibility of retroreflective sheeting. For example, Japanese PatentLaid-Open No. 173008/'93 discloses encapsulated lens retroreflectivesheeting having both retroreflectivity and light-storing luminositywherein a transparent resin layer is used as a support for partiallyembedding retroreflective microspherical lenses (i.e., microsphericallenses having a deposited metal film coating the approximatelyhemispherical surfaces thereof and hence exhibiting retroreflectivity)and a layer of a light-storing luminescent substance is disposed on theback surface (i.e., the surface opposite to the light incidence side) ofthe support. However, owing to the structure of this retroreflectivesheeting, the light radiating from the luminescent substance isintercepted by the embedded retroreflective microspherical lenses, sothat the amount of light emitted thereby is very small. Consequently,this retroreflective sheeting is totally unsatisfactory for the purposeof improving visibility.

Moreover, the specification of PCT International Application PublicationNo. WO93/14422 discloses photoluminescent encapsulated cube-cornerretroreflective sheeting which contains a phosphorescent pigment in thebonds for bonding the cube corner-forming surface to the support, andalso suggests a method for imparting fluorescent properties toencapsulated lens retroreflective sheeting. However, even in theretroreflective sheeting described in the specification of thisinternational application, the phosphorescent pigment fails to emit asufficient amount of light. Consequently, signs made of thisretroreflective sheeting will not have such a high degree of visibilitythat the information displayed thereby can be recognized from somedistance.

Furthermore, the specification of PCT International ApplicationPublication No. WO96/18920 discloses ultraviolet-excited luminousretroreflective sheeting of the encapsulated lens structure wherein thebonds at which a base sheet having retroreflective microspherical lensespartially embedded in a support is partly bonded to a protective filmare formed on the protective film or base sheet as anultraviolet-excited luminous layer by printing an ultraviolet-excitedluminous resin composition, and these bonds are then fused to the basesheet or protective film by the application of heat or bonded theretowith the aid of a suitable adhesive. Moreover, this specification alsosuggests ultraviolet-excited luminous retroreflective sheeting whereinan ultraviolet-excited luminous support is prepared by forming thesupport of an ultraviolet-excited luminous resin composition orproviding at least on the microspherical lens-embedding side of thesupport with an ultraviolet-excited luminous layer formed of anultraviolet-excited luminous resin composition, and this support ispartly heated and melt-formed by means of an embossing roll or the liketo form bonds for bonding the protective film partly to the base sheet.

However, the retroreflective sheeting described in the specification ofthe aforementioned WO96/18920 involves problems in that theultraviolet-excited luminous layer consists essentially of only thebonds for bonding the protective film to the base sheet and theproportion thereof to the total surface area of the retroreflectivesheeting is very small and in that the amount of luminescent substanceincorporated in the bonds cannot be increased so much. Consequently, ithas been found that the amount of light emitted by the luminescentsubstance tends to be insufficient and, moreover, the retroreflectivesheeting also has disadvantages such as poor adhesion of theultraviolet-excited luminous layer to the protective film and difficultyin forming an adhesive layer on the formed ultraviolet-excited luminouslayer.

On the other hand, several methods for embedding retroreflectivemicrospherical lenses in some part of a support are also known. Forexample, U.S. Pat. No. 4,075,049 discloses a method for the preparationof a base sheet which comprises the steps of embedding the approximatelyhemispherical parts of glass beads in a temporary support (e.g.,polyethylene-laminated paper) so as to form a mono-layer, depositing alightreflecting material on the glass bead-bearing surface thereof,forcing part of the glass bead layer into the polyethylene layer of thetemporary support by heating and pressing the glass bead-bearing side ofthe temporary support by means of a mold having a raised pattern, andpressing a support having an adhesive layer against the glassbead-bearing side of the temporary support to transfer the glass beadsnot buried in the polyethylene layer to the support.

However, the purpose of the method described in this U.S. patent lies inthe fact that, in the fabrication of encapsulated lens retroreflectivesheeting, the support of the base sheet is thermoformed by means of amold having the same raised pattern as the raised pattern of theaforesaid mold so as not to incorporate glass beads in the bonds forbonding a protective film to the base sheet. Although this method may beemployed in cases where it is desired to prevent a very small part ofthe glass bead layer from being transferred to the support, it is noteasy to prevent a large part (e.g., more than half) of the glass beadlayer from being transferred to the support and, therefore, thisproposed method is not considered to be suitable in such cases.

It is an object of the present invention to provide lens type functionalretroreflective sheeting which have both retroreflective regions andvisual functionality presenting regions and hence exhibit goodvisibility even at night or the like, as well as methods of producingthe same.

DISCLOSURE OF THE INVENTION

According to the present invention, there is provided lens typefunctional retroreflective sheeting comprising:

a base sheet consisting of a support comprising a functional resin layercontaining a resin component and a functional pigment havinglight-storing or fluorescent properties, microspherical lens-embeddingregions in which microspherical lenses with a deposited metal filmcoating the approximately hemispherical surfaces thereof are denselydistributed on the surface of the functional resin layer of the supportso as to form substantially a mono-layer, their approximatelyhemispherical surfaces coated with the deposited metal film are embeddedin the functional resin layer, and their approximately hemisphericalsurfaces not coated with the deposited metal film are exposed on thefunctional resin layer, and microspherical lens-free regions in whichessentially no microspherical lens is embedded and the functional resinlayer is exposed;

a transparent protective film disposed above that surface of the basesheet on which microspherical lenses are exposed; and

bonds at which the base sheet and the transparent protective film arepartly bonded together so as to hold a layer of air between the layer ofmicrospherical lenses and the transparent protective film,

the retroreflective sheeting having retroreflective regions comprisingthose parts of the microspherical lens-embedding regions in which thebonds are not formed, and visual functionality presenting regionscomprising at least the microspherical lens-free regions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example of a schematic plan view of encapsulated lensfunctional retroreflective sheeting in accordance with a preferredembodiment of the present invention as viewed from the light incidenceside;

FIG. 2 is a schematic sectional view taken along line A--A in FIG. 1;

FIG. 3 is a plan view of a temporary support having apertures formed bycutting out some parts thereof and affording a typical example of thetemporary support used in the fabrication of lens type functionalretroreflective sheeting in accordance with the present invention;

FIG. 4 is a schematic sectional view taken along line B--B in FIG. 3;

FIG. 5 is a plan view of a temporary support having a temporarymicrospherical lens-embedding layer formed in some parts thereof andaffording another typical example of the temporary support used in thefabrication of lens type functional retroreflective sheeting inaccordance with the present invention;

FIG. 6 is a sectional view taken along line C--C in FIG. 5;

FIG. 7 is a series of schematic sectional views illustrating severalsteps of a method of producing lens type functional retroreflectivesheeting in accordance with the present invention by using the temporarysupport illustrated in FIGS. 3 and 4;

FIG. 8 is a series of schematic sectional views illustrating severalsteps of a method of producing lens type functional retroreflectivesheeting in accordance with the present invention by using the temporarysupport illustrated in FIGS. 5 and 6; and

FIG. 9 is a series of schematic sectional views illustrating severalsteps of a method of producing lens type functional retroreflectivesheeting in accordance with the present invention by using an ordinarytemporary support and a relief mold (e.g., an embossing roll), insteadof using the special temporary supports illustrated in FIGS. 3 to 6.

DETAILED DESCRIPTION OF THE INVENTION

The retroreflective sheeting of the present invention and the methods ofproducing the same are more specifically described hereinbelow withreference to FIGS. 1 to 9.

FIG. 1 is a plan view of encapsulated lens functional retroreflectivesheeting affording a typical example of the lens type functionalretroreflective sheeting of the present invention, and FIG. 2 is asectional view taken along line A--A in FIG. 1.

In FIGS. 1 and 2, numerals 1 and 2 designate visual functionalitypresenting regions and retroreflective regions, respectively. Numeral 3designates bonds, in the form of continuous lines, at which a base sheetand a transparent protective film 6 are bonded together. Thus,hermetically sealed microcelIs (i.e., capsules) 8 having a layer of air9 enclosed therein are defined by bonds 3, transparent protective film 6and base sheet 12. Moreover, bonds 3 shown in FIG. 2 have been formed bypartially thermoforming a functional resin layer 7 according to apreferred embodiment of the present invention, and these bonds 3themselves form part of visual functionality presenting regions 1. Asupport 11 consists essentially of functional resin layer 7 and, ifnecessary, may include a reinforcing layer 10 laminated to the backsurface of functional resin layer 7. Base sheet 12 consists of support11, microspherical lens-embedding regions formed on the light incidenceside surface of functional resin layer 7 of support 11 and havingembedded therein and supported thereby microspherical lenses 4 whichhave a deposited metal film 5 coating the approximately hemisphericalsurfaces thereof and hence exhibit retroreflectivity, and microsphericallens-free regions in which substantially no microspherical lens isembedded and the functional resin layer is exposed. In themicrospherical lens-embedding regions, microspherical lenses 4 aredensely distributed so as to form substantially a monolayer and theirapproximately hemispherical surfaces coated with deposited metal film 5are embedded in and supported by functional resin layer 7. Consequently,their approximately hemispherical surfaces not coated with depositedmetal film 5 are exposed on functional resin layer 7 and exhibitretroreflectivity. Of these microspherical lens-embedding regions, theparts in which bonds 3 are formed loses its retroreflectivity becausethe microspherical lenses are buried therein, but the other partsenclosed in capsules 8 constitute retroreflective regions 2. On theother hand, the microspherical lens-free regions positioned withincapsules 8, together with bonds 3, constitute visual functionalitypresenting regions 1.

Functional resin layer 7 constituting support 11 contains a resincomponent and a functional pigment having light-storing or fluorescentproperties. Examples of suitable functional pigments includelight-storing pigments and ultraviolet-excited fluorescent pigments.

Light-storing pigments are pigments which store the energy of sunlightin the daytime and light radiating from fluorescent lamps, automobileheadlamps or the like at night, and emit light gradually even in thedark after the irradiation with light is discontinued. No particularlimitation is placed on the type of light-storing pigment used in thepresent invention, and any of organic light-storing pigments andinorganic light-storing pigments may be used. However, from theviewpoint of light-storing performance, inorganic light-storing pigmentsand, in particular, oxide type light-storing pigments are preferablyused. Especially preferred are light-storing pigments comprising matrixcrystals of a metal oxide of the general formula MAI₂ O₄ (in which Mrepresents at least one alkaline earth metal) containing rare earthmetal atoms as an activator in an atomic fraction of 1×10⁻⁶ to 0.2, morepreferably 1×10⁻⁵ to 0.15, based on the total number of alkaline earthmetal (M) atoms and rare earth metal atoms.

As the aforesaid alkaline earth metal, it is preferable to use at leastone metal selected from the group consisting of Ca, Ba and Sr. Moreover,the rare earth metal can be at least one metal selected from the groupconsisting of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yband Lu. If necessary, the light-storing pigment may contain acoactivator comprising at least one metal selected from the groupconsisting of Mn, Sn and Bi, in an atomic fraction of 1×10⁻⁶ to 0.2,more preferably 1×10⁻⁵ to 0.15, based on the total number of alkalineearth metal (M) atoms, rare earth metal atoms and coactivator atoms.

Examples of such light-storing pigments include SrAl₂ O₄ :Eu, SrAl₂ O₄:Eu, Dy, SrAl₂ O₄ :Eu, Nd, SrAl₂ O₄ :Eu, Pr, SrAl₂ O₄ :Eu, Sm, SrAl₂ O₄:Eu, Tb, SrAl₂ O₄ :Eu, Ho, SrAl₂ O₄ :Eu, Mn, SrAl₂ O₄ : Eu, Sn, SrAl₂ O₄:Eu, Bi, CaAl₂ O₄ :Eu, Nd, CaAl₂ O₄ :Eu, Sm, CaAl₂ O₄ :Eu, Tm, CaAl₂ O₄:Eu, Nd, La, CaAl₂ O₄ :Eu, Nd, Ce, CaAl₂ O₄ :Eu, Nd, Pr, CaAl₂ O₄ :Eu,Nd, Sm, CaAl₂ O₄ :Eu, Nd, Gd, CaAl₂ O₄ :Eu, Nd, Tb, CaAl₂ O₄ :Eu, Nd,Dy, CaAl₂ O₄ :Eu, Nd, Ho, CaAl₂ O₄ :Eu, Nd, Er, CaAl₂ O₄ :Eu, Nd, Tm,CaAl₂ O₄ :Eu, Nd, Yb, CaAl₂ O₄ :Eu, Nd, Lu, CaAl₂ O₄ :Eu, Nd, Mn, CaAl₂O₄ :Eu, Nd, Sn, CaAl₂ O₄ :Eu, Nd, Bi, Ca₀.9 Sr₀.1 Al₂ O₄ : Eu, Nd, La,Ca₀.9 Sr₀.1 Al₂ O₄ :Eu, Nd, Dy, Ca₀.7 Sr₀.3 Al₂ O₄ :Eu, Nd, Dy, Ca₀.9Sr₀.1 Al₂ O₄ :Eu, Nd, Ho and Ca₀.7 Sr₀.3 Al₂ O₄ :Eu, Nd, Ho. Theselight-storing pigments may be used alone or in admixture of two or more.

These light-storing pigments should generally have an afterglowcharacteristic of not less than 150 mcd/m², preferably not less than 200mcd/m², and more preferably not less than 250 mcd/m², as measuredaccording to the following method.

Measurement of Afterglow Characteristic:

0.05 g of a light-storing pigment powder sample is weighed out, placedin an aluminum sample pan having an inner diameter of 8 mm, and allowedto stand in the dark for about 12 hours until the afterglow disappears.Thereafter, the sample is irradiated with a D65 common light source for30 minutes at an iiluminance of 1,000 Ix, and allowed to stand in thedark for 10 minutes. Then, using a luminance meter ("LS-100";manufactured by Minoruta Camera Co., Ltd.), the amount of light emittedby the sample is measured at a distance of about 30 cm from the sampleand regarded as its afterglow characteristic.

The ultraviolet-excited fluorescent pigment which can be used as afunctional pigment in the present invention is a pigment of the typeemitting light upon excitation with the radiant energy of ultravioletradiation. No particular limitation is placed on the type of theultraviolet-excited fluorescent pigment used, and it may be arbitrarilyselected from various fluorescent pigments including, for example,organic fluorescent pigments generally having relatively high lighttransmission properties, such as naphthotriazole pigments andbenzoxazole pigments; and inorganic fluorescent pigments generallyimpervious to light, such as inorganic metallic salt pigments, metalhalide pigments, metal oxide pigments and metal sulfide pigments.Preferred examples of the ultraviolet-excited fluorescent pigment areones which emits visible light upon irradiation with ultravioletradiation having a wavelength in the range of 250 to 400 nm.

Examples of the aforesaid organic fluorescent pigments includediaminostilbene, uranine, thioflavine T, eosine, rhodamine B andacridine orange; and organic pigments based on diphenylmethane dyes,triphenylmethane dyes, xanthene dyes, thiazine dyes, thiazole dyes andthe like. These organic fluorescent pigments may be used alone or inadmixture of two or more.

Examples of the inorganic fluorescent pigments include redlight-emitting inorganic fluorescent pigments such as Y₂ O₃ :Eu,Y(P,V)O₄ :Eu, Y₂ O₃ S:Eu, 0.5MgF₂ ·3.5MgO·GeO₂ :Mn, YVO₄ :Eu and(Y,Gd)BO₃ :Eu; green light-emitting inorganic fluorescent pigments suchas Zn₂ GeO₄ :Mn, ZnO:Zn, ZnS:Cu, ZnS:(Cu,Al), (Zn,Cd)S: (Cu,Al), ZnS:(Cu,Au,Al), Zn₂ SiO₄ :Mn, ZnS:(Cu,Ag), (Zn,Cd)S:Cu, Gd₂ O₂ S:Tb, La₂ O₂S:Tb, Y₂ SiO₅ :(Ce,Tb), CeMgAl₁₁ O₁₉ :Tb, ZnS:(Cu,Co), LaOBr:(Tb,Tm),La₂ O₂ S:Tb and BaMg₂ Al₁₆ O₂₇ :(Eu, Mu); and blue light-emittinginorganic fluorescent pigments such as Sr₅ (PO₄)₃ Cl:Eu, BaMg₂ Al₁₆ O₂₇:Eu, BaMgAl₁₀ O₁₇ :Eu, ZnS:Ag, CaWO₄, Y₂ SiO₅ : Ce, ZnS:(Ag, Ga, Cl),Sr₂ P₂ O₇ :Eu, CaS:Bi and CaSrS:Bi. Of these inorganic fluorescentpigments, those emitting light of the same color may be used alone or inadmixture. Alternatively, in order to emit light in a desired tone ofcolor, those emitting light of different colors may be used in admixtureof two or more.

Since inorganic fluorescent pigments are generally more excellent inlight resistance, thermal resistance, solvent resistance and the likethan organic fluorescent pigments, inorganic fluorescent pigments arepreferably used in cases where the resulting ultraviolet-excitedretroreflective sheeting is to be used chiefly out of doors. Moreover,among inorganic fluorescent pigments, the above-described greenlight-emitting, red light-emitting and blue light-emitting inorganicfluorescent pigments may preferably be used because of the specialadvantage that they exhibit a high luminous intensity upon excitationwith ultraviolet radiation and afford good visibility to viewers atnight.

The inorganic fluorescent pigments should preferably have a particlediameter distribution containing 80% by weight or more of particleshaving a diameter of not greater than 25 μm, because they can be easilydispersed in the resin component and the resulting functional resinlayer has good smoothness and few defects such as pinholes.

Where a light-storing pigment is used as the functional pigment in thepractice of the present invention, the functional resin layer is alight-storing luminous resin layer and the visual functionalitypresenting regions are light-storing luminous regions. Thislight-storing luminous resin layer contains a light-storing pigment anda resin component, and the light-storing pigment may generally bepresent in an amount of 100 to 900 parts by weight, preferably 150 to800 parts by weight, and more preferably 200 to 700 parts by weight, per100 parts by weight of the resin component.

Where an ultraviolet-excited fluorescent pigment is used as thefunctional pigment in the practice of the present invention, thefunctional resin layer is an ultraviolet-excited luminous resin layerand the visual functionality presenting regions are ultraviolet-excitedluminous regions. This ultraviolet-excited luminous resin layer containsan ultraviolet-excited fluorescent pigment and a resin component, andthe ultraviolet-excited fluorescent pigment may generally be present inan amount of 10 to 600 parts by weight, preferably 50 to 400 parts byweight, and more preferbly 100 to 300 parts by weight, per 100 parts byweight of the resin component.

The resin components which can be used for the functional resin layer inthe present invention include, for example, acrylic resins, polyurethaneresins, polyester resins, vinyl chloride resins, vinyl acetate resins,polyolefin resins, fluororesins and polyamide resins. However, from theviewpoint of weather resistance and thermoformability, acrylic resinsare preferably used.

If necessary, the functional resin layer may also contain, in additionto the functional pigment and the resin component, a crosslinking agentsuch as an isocyanate, melamine or metallic crosslinking agent. Thus, athree-dimensional crosslinked structure may be introduced into the resincomponent. However, it is preferable that parts of functional resinlayer 7 can be thermally deformed by the application of heat andpressure to form bonds 3 at which base sheet 12 and transparentprotective film 6 are partly bonded together. Accordingly, at leastduring the formation of bonds 3, functional resin layer 7 shouldpreferably retain such a degree of fluidity as to permit the aforesaidthermoforming.

If necessary, functional resin layer 7 may further contain variousfillers such as cellulosic resins, internally crosslinked microsphericalresins, various colorants and thermal stabilizers. With considerationfor the degree of functionality presentation (e.g., the magnitude ofluminous intensity) when functional resin layer 7 acts as functionalitypresenting regions, the ease of thermal deformation in the bond-formingstep which will be described later, and the like, the thickness offunctional resin layer 7 is usually in the range of about 20 to about250 μm and preferably about 30 to about 200 μm.

Support 11 used in the present invention may consist of functional resinlayer 7 alone. Alternatively, if necessary, a reinforcing layer 10 maybe laminated to the back side of functional resin layer 7 as illustratedin FIG. 2.

This reinforcing layer 10 may usually comprise a layer of a crosslinkedresin. The resin component used may be suitably chosen from the resinswhich were enumerated above for the functional resin layer. Thecrosslinking agent used to crosslink the resin may also be the same asdescribed above for the functional resin layer. Moreover, if necessary,the reinforcing layer may further contain white pigments such astitanium dioxide, extenders such as calcium carbonate and clay, variousfillers described above for the functional resin layer, and the like.

With consideration for the weather resistance and mechanical strength ofthe resulting lens type functional retroreflective sheeting, the shapestability of the thermoformed parts, and the like, it is convenient thatthe thickness of reinforcing layer 10 is usually in the range of 10 to80 μm and preferably 20 to 60 μm.

Moreover, if necessary, support 11 used in the present invention mayhave an intermediate layer disposed between functional resin layer 7 andreinforcing layer 10 for improving the adhesion of these layers. Thus,the overall thickness of support 11 used in the present invention isusually in the range of about 30 to bout 300 μm and preferably about 60to about 250 μm.

In the present invention, the light incidence side surface of functionalresin layer 7 of the support has formed therein microsphericallens-embedding regions in which retroreflective microspherical lenses 4(i.e., microspherical lenses 4 whose approximately hemisphericalsurfaces are coated with deposited metal film 5) are embedded andsupported, and microspherical lens-free regions in which substantiallyno microspherical lens is embedded and the functional resin layer isexposed. The microspherical lens-embedding regions are formed on partsof the light incidence side surface of functional resin layer 7 ofsupport 11 so as to have any desired shapes and areas. In thesemicrospherical lens-embedding regions, the microspherical lenses arepresent in such a state that they are densely distributed on the surfaceof the functional resin layer of the support so as to form substantiallya mono-layer, their approximately hemispherical surfaces coated with thedeposited metal film are embedded in the functional resin layer, andtheir approximately hemispherical surfaces not coated with the depositedmetal film are exposed on the functional resin layer.

The embedded microspherical lenses 4 generally have an average particlediameter of 10 to 100 μm, preferably 30 to 80 μm, and more preferably 40to 70 μm. The microspherical lenses should desirably have a refractiveindex of about 1.9, and glass beads are usually used.

In the present invention, no particular limitation is placed on thematerial of transparent protective film 6 disposed above that surface ofbase sheet 12 on which microspherical lenses 4 are exposed, providedthat it has a total light transmittance of at least 20% or greater andpreferably 40% or greater and it has a certain degree of flexibility.Useful materials include, for example, films made of acrylic resins,fluororesins, polyurethane resins, vinyl chloride resins, polycarbonateresins, polyester resins and polyolefin resins.

Moreover, transparent protective film 6 should preferably be unoriented.The reason for this is that, although a uniaxially or biaxially orientedfilm has improved mechanical strength, the residual strain in the filmmay detract from the durability of the resulting retroreflectivesheeting. The thickness of transparent protective film 6 may vary widelyaccording to the intended use of the resulting lens type functionalretroreflective sheeting and the like. However, it is usually determinedso as to be in the range of 20 to 200 μm, preferably 40 to 150 μm, andmore preferably 50 to 100 μm.

In the present invention, base sheet 12 and transparent protective film6 are partly bonded by bonds 3 so that a layer of air 9 is held betweenthe layer of retroreflective microspherical lenses and transparentprotective film 6. No particular limitation is placed on the method forforming these bonds 3. For example, they may be formed by printing asuitable bond-forming resin composition according to a screen printingor gravure printing technique. In this case, the bond-forming resincomposition may be one consisting essentially of a resin component andhaving light transmission properties. However, if necessary, thebond-forming resin composition may contain the same functional pigmentand other additives as used in functional resin layer 7. Moreover,similarly to functional resin layer 7, any of various crosslinkingagents may be incorporated into the bond-forming resin composition tointroduce a three-dimensional crosslinked structure into the resincomponent. No particular limitation is placed on the height of bonds 3so formed, provided that micropherical lenses 4 can be completely buriedtherein. It is convenient that the thickness of bonds 3 is generally inthe range of 10 to 100 μm, preferably 30 to 80 μm, and more preferably40 to 70 μm.

Alternatively, bonds 3 may also be formed by partially thermoformingfunctional resin layer 7. One example of the method for forming bonds 3in this manner is such that base sheet 12 is heated by means of a reliefmold (e.g., an embossing roll) disposed on the back side of base sheet12 and, at the same time, pressed between this relief mold and a back-upmeans (e.g., a rubber roll) disposed oppositely on the side oftransparent protective film 6.

Of these methods for forming bonds 3, that based on thermoforming ispreferred because a stabilized bonding strength is obtained in bondingtransparent protective film 6 to base sheet 12 and because the equipmentused for this purpose is simple and its operating conditions can beeasily controlled.

No particular limitation is placed on the width of bonds 3 at whichtransparent protective film 6 is bonded to base sheet 12, provided thatadequate adhesion is achieved between transparent protective film 6 andbase sheet 12 and a predetermined proportion of retroreflective regionscan be secured. However, it is desirable that, when viewed from thelight incidence side, the width of bonds 3 is generally in the range ofabout 200 to about 1,000 μm, preferably about 250 to about 900 μm, andmore preferably about 300 to about 800 μm.

When bonds 3 are formed in the form of continuous lines as illustratedin FIG. 1, hermetically sealed microcells (i.e., capsules) having alayer of air 9 enclosed therein are defined by bonds 3, transparentprotective film 6 and base sheet 12. This is preferable in that, even ifthe resulting lens type functional retroreflective sheeting is usedoutdoors for a long period of time, the deterioration of its properties(e.g., retroreflectivity and visual functionality such as light-storingor ultraviolet-excited luminous properties) due to the infiltration ofrainwater or the like into the capsules is minimized.

When viewed from the light incidence side, the size of the aforesaidcapsules 8 should generally be in the range of about 3 to about 100 mm²,preferably about 5 to about 70 mm², and more preferably about 7 to about50 mm², in order to maintain the surface smoothness of the lens typefunctional retroreflective sheeting by minimizing the deformation of theprotective film itself which tends to result from the formation ofcapsules, and in order to minimize the amount of dirt, dust, rainwaterand the like entering the broken capsules through the cut ends when thelens type functional retroreflective sheeting is cut into pieces ofdesired shape and used outdoors.

Alternatively, bonds 3 may be formed in the form of dots ordiscontinuous lines. In this case, however, it is desirable to cut theresulting lens type functional retroreflective sheeting into piece ofdesired shape according to its intended use and seal their periphery bya suitable means, so that rainwater or the like may be prevented frominfiltrating into the spaces between transparent protective film 6 andthe support during outdoor use. To this end, it is preferable to formfunctional resin layer 7 of a thermoplastic resin and heat-seal theperiphery prior to use.

The resulting lens type functional retroreflective sheeting of thepresent invention has retroreflective regions 2 comprisingmicrospherical lens-embedding regions having a layer of retroreflectivemicrospherical lenses embedded therein, exclusive of bonds 3, andcovered on the light incidence side with transparent protective film 6through the intervention of a layer of air 9, and visual functionalitypresenting regions 1 (light-storing luminous regions orultraviolet-excited luminous regions) comprising bonds 3 andmicrospherical lens-free regions. In the case of encapsulated lensfunctional retroreflective sheeting in which bonds 3 are formed in theform of continuous lines as illustrated in FIG. 1, the parts of capsules8 in which a layer of microspherical lenses 4 is enclosed constituteretroreflective regions 2, and the remaining parts of capsules 8 andbonds 3 constitute visual functionality presenting regions 1.

In the lens type functional retroreflective sheeting of the presentinvention, the proportions of the area of retroreflective regions 2 andthe area of visual functionality presenting regions 1 cannot necessarilybe defined to be fixed because they may vary, for example, according tothe intended use of the sheeting, the functionality to be presented, andthe type of the functionality (i.e., light-storing orultraviolet-excited luminous properties). However, from the viewpoint ofthe balance between retroreflectivity and the degree of visualfunctionality presentation (e.g., luminous intensity) and other factors,it is generally suitable that the proportion of the area ofretroreflective regions 2 is usually in the range of 10 to 70%,preferably 15 to 50%, and the proportion of the area of visualfunctionality presenting regions 1 is usually in the range of 30 to 90%,preferably 50 to 85%, based on the total area of the light incidenceside surface of the retroreflective sheeting.

More specifically, where visual functionality presenting regions 1 arelight-storing luminous regions, the proportion of the area of theretroreflective regions may generally be in the range of 10 to 50%,preferably 15 to 40%, and the proportion of the area of thelight-storing luminous regions may generally be in the range of 90 to50%, preferably 85 to 60%, based on the total area of the lightincidence side surface of the retroreflective sheeting. On the otherhand, where visual functionality presenting regions 1 areultraviolet-excited luminous regions, the proportion of the area of theretroreflective regions may generally be in the range of 10 to 70%,preferably 15 to 60%, and more preferably 30 to 50%, and the proportionof the area of the ultraviolet-excited luminous regions may generally bein the range of 90 to 30%, preferably 85 to 40%, and more preferably 70to 50%, based on the total area of the light incidence side surface ofthe retroreflective sheeting.

The above-described lens type functional retroreflective sheeting of thepresent invention may be made, for example, according to a method(hereinafter referred to as "the method of the present invention")comprising the steps of:

(a) providing a temporary support having been subjected to a treatmentfor preventing microspherical lenses from being temporarily embedded insome parts thereof, supporting a large number of microspherical lenseson those parts of the temporary support which allow microsphericallenses to be temporarily embedded, in such a way that the microsphericallenses are densely distributed so as to form substantially a mono-layerand the approximately hemispherical surfaces thereof are embedded in thetemporary support, and thereby preparing a temporary microsphericallens-supporting sheet comprising the temporary support having themicrospherical lenses embedded in some parts thereof;

(b) depositing a metal on the microspherical lens-bearing surface of thetemporary microspherical lens-supporting sheet to form a deposited metalfilm on those approximately hemispherical surfaces of the microsphericallenses which project above the temporary support;

(c) separately preparing a support having a functional resin layercontaining a resin component and a functional pigment havinglight-storing or fluorescent properties, superposing the support on thetemporary microspherical lens-supporting sheet in such a way that thefunctional resin layer side of the support comes into contact with themicrospherical lens surfaces projecting above the temporarymicrospherical lens-supporting sheet and having the deposited metalfilm, and pressing and laminating the resulting assembly to embed thedeposited metal film-bearing approximately hemispherical surfaces of themicrospherical lenses in the functional resin layer of the support;

(d) stripping the temporary support from the resulting laminate totransfer the microspherical lenses to the functional resin layer of thesupport; and

(e) superposing a transparent protective film on the resulting basesheet having the microspherical lenses embedded in the functional resinlayer, in such a way that the transparent protective film rests on thosedeposited metal film-free approximately hemispherical surfaces of themicrospherical lenses which project above the base sheet, and using arelief mold disposed on the back side of the base sheet to partiallythermoform the functional resin layer of the base sheet by theapplication of heat and pressure and thereby form bonds for bonding thetransparent protective film partly to the base sheet.

FIGS. 3 and 5 are plan views showing typical examples of the temporarysupport having been subjected to a treatment for preventingmicrospherical lenses from being temporarily embedded in some partsthereof which support is used in the above-described step (a) for thepurpose of producing the lens type functional retroreflective sheetingof the present invention. FIGS. 4 and 6 are sectional views taken alongline B--B in FIG. 3 and line C--C in FIG. 5, respectively.

The temporary support shown in FIGS. 3 and 4 is a temporary supporthaving apertures formed by cutting out some parts thereof as "thetreatment for preventing microspherical lenses from being temporarilyembedded in some parts thereof." In FIGS. 3 and 4, temporary support 15consists of a temporary microspherical lens-embedding layer 13 forembedding microspherical lenses 4, and a backing layer 14 for supportingtemporary microspherical lens-embedding layer 13, and has apertures 16formed therein.

No particular limitation is placed on the material of this temporarysupport 15, provided that it performs the function of embeddingmicrospherical lenses 4. Although any material that is known per se maybe used, polyethylene-laminated paper using a polyethylene film astemporary microspherical lens-embedding layer 13 and paper as backinglayer 14 is most preferred. Moreover, no particular limitation is placedon the method for forming apertures 16 in some parts of temporarysupport 15, and any of various methods such as rotary die cutting, rolldie cutting and blanking may be mentioned. Furthermore, no particularlimitation is placed on the shape of apertures 16, and any desiredshapes may be used alone or in suitable combination. However, circularapertures are preferred from the viewpoint of the strength of thetemporary support. From the viewpoint of the strength of the temporarysupport and the balance between the retroreflectivity of the resultinglens type functional retroreflective sheeting and the degree of visualfunctionality presented thereby, the area of apertures 16 should usuallybe in the range of 30 to 70% based on the surface area of the temporarysupport before cutting out.

The temporary support illustrated in FIGS. 5 and 6 is a temporarysupport having a temporary microspherical lens-embedding layer 13 formedin some parts thereof as "the treatment for preventing microsphericallenses from being temporarily embedded in some parts thereof." In FIGS.5 and 6, temporary support 15 consists of a temporary microsphericallens-embedding layer 13 formed in some parts thereof to embedmicrospherical lenses 4, and a backing layer 14 for supporting temporarymicrospherical lens-embedding layer 13.

Similarly to the embodiment described above in connection with FIGS. 3and 4, no particular limitation is placed on the material of temporarymicrospherical lens-embedding layer 13 in this temporary support 15,provided that it performs the function of embedding microsphericallenses 4. Paper may be used as backing layer 14. Moreover, no particularlimitation is placed on the type of the resin used for the formation oftemporary microspherical lens-embedding layer 13, and thermoplasticresins such as vinyl chloride resins, acrylic resins, polyvinyl alcoholresins, polyvinyl butyral resins, vinylidene chloride resins,polyurethane resins, cellulosic resins and polyester resins may be used.However, acrylic resins, polyvinyl alcohol resins, vinylidene chlorideresins and the like are preferably used, for example, because theyfacilitate the formation of a temporary microspherical lens-embeddinglayer and they have a low softening temperature and can hence besufficiently deformed by the application of heat to embed microsphericallenses.

It is usually convenient that the formation of the aforesaid temporarymicrospherical lens-embedding layer 13 is carried out according to acontinuous printing technique such as rotary screen printing or gravureprinting. No limitation is placed on the shape of temporarymicrospherical lens-embedding layer 13, and any desired shape may besuitably chosen. From the viewpoint of the balance between theretroreflectivity of the resulting lens type functional retroreflectivesheeting and the degree of visual functionality presented thereby, thearea of the parts in which temporary microspherical lens-embedding layer13 is formed should usually be in the range of 10 to 70% based on thesurface area of the temporary support.

FIG. 7 is a series of schematic sectional views illustrating severalsteps of the method of the present invention in which lens typefunctional retroreflective sheeting is made by using the temporarysupport illustrated in FIGS. 3 and 4.

FIG. 7(a) illustrates step (a) in the method of the present invention,i.e., the step of preparing a temporary microspherical lens-supportingsheet by embedding microspherical lenses in temporary support 15 havingapertures 16 formed by cutting out some parts thereof.

Specifically, for example, polyethylene-laminated paper 15 havingapertures 16 formed therein is heated to about 110° C., and glass beads4 serving as microspherical lenses are densely scattered over thesoftened polyethylene film 13 thereof. Then, using nip rolls or thelike, glass beads 4 are pressed into polyethylene film 13 in such a waythat they are embedded therein to a depth equal to about 1/3 to 1/2 ofthe diameter thereof and they are densely distributed so as to formsubstantially a mono-layer. In this step, glass beads 4 are not embeddedin apertures 16 of temporary support 15. Consequently, afterpolyethylene film 13 is cooled, glass beads present in apertures 16,together with unembedded excess glass beads remaining on polyethylenefilm 13, are removed from polyethylene-laminated paper 15 by a suitablemeans such as vibration, air blowing or suction. Thus, there is obtaineda temporary glass bead- (or microspherical lens-)supporting sheet 17 inwhich, in the parts other than apertures 16, glass beads 4 are embeddedin such a way that they are densely distributed so as to form amono-layer.

FIG. 7(b) illustrates step (b) in the method of the present invention,i.e., the metal deposition step. In this step, according to a vacuumevaporation process or the like, a metal (e.g., aluminum) used as alight reflecting element is deposited on that side of temporarymicrospherical lens-supporting sheet 17 to which microspherical lenses 4are attached, so that a deposited metal film 5 is formed. No particularlimitation is placed on the type of the metal used in this step,provided that it can be deposited by vacuum evaporation. However,aluminum is most preferred because it has conventionally been used inretroreflective sheeting and can readily be obtained at low cost.

FIG. 7(c) illustrates step (c) in the method of the present invention,i.e., the step of preparing a support 11 and embedding themicrospherical lenses therein.

Specifically, support 11 is prepared in the following manner: A processfilm 18 comprising, for example, a polyethylene terephthalate film whosesurfaces have been made releasable by treatment with a silicone resinrelease agent is provided, and a reinforcing layer-forming resincomposition containing a crosslinkable resin component (e.g., ahydroxyl-containing acrylic resin) and a crosslinking agent (e.g., anisocyanate crosslinking agent) is applied onto process film 18 and driedto form a reinforcing layer 10. Then, a functional resin layer-formingcomposition containing a functional pigment (e.g., a light-storingpigment or an ultraviolet-excited fluorescent pigment) and a resincomponent (e.g., an acrylic resin) is applied directly onto reinforcinglayer 10 and dried to form a functional resin layer 7, or a functionalresin layer 7 obtained by applying the functional resin layer-formingcomposition onto another process film and drying it is laminated toreinforcing layer 10. Thus, there is obtained a support 11 comprising alaminate of functional resin layer 7 and reinforcing layer 10.

Then, the resulting support 11 is superposed on temporary microsphericallens-supporting sheet 17 having glass beads embedded in the parts otherthan apertures 16 as prepared in step (a), in such a way that functionalresin layer 7 of support 11 comes into contact with the deposited metalfilm (5)-bearing surfaces of microspherical lenses 4 projecting abovetemporary microspherical lens-supporting sheet 17. While the resultingassembly is heated, if necessary, to soften functional resin layer 7,this assembly is pressed and laminated by means of nip rolls or the liketo embed the deposited metal film (5)-bearing approximatelyhemispherical surfaces of microspherical lenses 4 in functional resinlayer 7 to a depth equal to about 1/6 to 1/2 of the diameter thereof. Inthis step, the deposited metal film present on temporary microsphericallens-supporting sheet 17 between microspherical lenses 4 should beprevented from coming into direct contact with the surface of functionalresin layer 7 so that the deposited metal film may not be transferred tothe surface of functional resin layer 7.

Specifically, this can be accomplished, for example, by superposingsupport 11 on temporary microspherical lens-supporting sheet 17 so as toleave a space between functional resin layer 7 and temporarymicrospherical lens-supporting sheet 17; or by forming a film forpreventing the deposited metal film present between microsphericallenses 4 from being transferred to the surface of functional resin layer7 (e.g., a resin film comprising an acrylic resin or other resincontaining a silane coupling agent) before superposing functional resinlayer 7 on the metal-coated microspherical lens-bearing surface oftemporary microspherical lens-supporting sheet 17. Since no sphericallens is present in apertures 16 of temporary microsphericallens-supporting sheet 17, functional resin layer 7 is divided intoregions in which microspherical lenses 4 are embedded and regions inwhich no microspherical lens is embedded.

FIG. 7(d) illustrates step (d) in the method of the present invention,i.e., the temporary support stripping step. In this step, according to amethod well known in this technical field, temporary support 15 isstripped from the laminate obtained in step (c). Thus, there is obtaineda base sheet 12 having both microspherical lens-embedding regions inwhich the deposited metal film (5)-bearing approximately hemisphericalparts of microspherical lenses 4 are embedded in functional resin layer7 and the deposited metal film (5)-free approximately hemisphericalsurfaces of microspherical lenses 4 project above functional resin layer7, and microspherical lens-free regions in which no microspherical lensis embedded and the surface of functional resin layer 7 is exposed.

FIG. 7(e) illustrates step (e) in the method of the present invention,i.e., the bond forming step. A transparent protective film 6 issuperposed on the microspherical lens-bearing side of the aforesaid basesheet 12 obtained in step (d). Then, base sheet 12 is heated by means ofa relief mold (e.g., an embossing roll 19) disposed on the back side ofbase sheet 12 [i.e., on the reinforcing layer (10) side of base sheet 12in FIG. 7(e)] and, at the same time, pressed between this relief moldand a back-up means (e.g., a rubber roll 20) disposed oppositely on theside of transparent protective film 6. Consequently, parts of functionalresin layer 7 of base sheet 12 are thermoformed to form bonds forbonding transparent protective film 6 partly to base sheet 12. Thus,there is obtained lens type functional retroreflective sheeting inaccordance with the present invention.

FIG. 8 is a series of schematic sectional views illustrating severalsteps of the method of the present invention in which lens typefunctional retroreflective sheeting is made by using the temporarysupport illustrated in FIGS. 5 and 6;

FIG. 8(a) illustrates step (a) in the method of the present invention,i.e., the step of preparing a temporary microspherical lens-supportingsheet by embedding microspherical lenses in temporary support 15 havingtemporary microspherical lens-embedding layer 13 formed in some partsthereof.

Specifically, a temporary support 15 comprising kraft paper 14 having atemporary microspherical lens-embedding layer 13 formed on some partsthereof so as to have a suitable shape (e.g., the shape of squares asviewed from the light incidence side) is provided. This temporarysupport 15 is heated to about 100° C., and glass beads 4 serving asmicrospherical lenses are densely scattered thereover. Then, using niprolls or the like, glass beads 4 are pressed into temporarymicrospherical lens-embedding layer 13 in such a way that they areembedded therein to a depth equal to about 1/3 to 1/2 of the diameterthereof and they are densely distributed so as to form substantially amono-layer. In this step, glass beads 4 are not embedded in those partsof temporary support 15 in which temporary microspherical lens-embeddinglayer 13 is not formed. Consequently, after the resin of this temporarymicrospherical lens-embedding layer 13 is cooled, glass beads present inthese parts, together with unembedded excess glass beads remaining ontemporary microspherical lens-embedding layer 13, are removed fromtemporary support by a suitable means such as vibration, air blowing orsuction. Thus, there is obtained a temporary glass bead- (ormicrospherical lens-)supporting sheet 17 in which, only in the partsbearing temporary microspherical lens-embedding layer 13, glass beads 4are embedded in such a way that they are densely distributed so as toform a mono-layer.

FIG. 8(b) illustrates step (b) in the method of the present invention,i.e., the metal deposition step. Specifically, this step is carried outin substantially the same manner as described previously in connectionwith FIG. 7(b).

FIG. 8(c) illustrates step (c) in the method of the present invention,i.e., the step of preparing a support 11 and embedding themicrospherical lenses therein. Specifically, this step is carried out inthe same manner as described previously in connection with FIG. 7(c),except that temporary glass bead-supporting sheet 17 having glass beadsembedded only in the parts bearing temporary microsphericallens-embedding layer 13 as prepared with reference to FIG. 8(a) is usedin place of temporary microspherical lens-supporting sheet 17 havingglass beads embedded in the parts other than apertures 16 as preparedwith reference to FIG. 7(a).

FIGS. 8(d) and 8(e) illustrate steps (d) and (e) in the method of thepresent invention, i.e., the temporary support stripping step and thebond forming step. These steps may be carried out in exactly the samemanner as described previously in connection with FIGS. 7(d) and 7(e).Thus, there is obtained lens type functional retroreflective sheeting inaccordance with the present invention.

On the other hand, FIG. 9 is a series of schematic sectional viewsillustrating several steps of another method of producing lens typefunctional retroreflective sheeting in accordance with the presentinvention by using an ordinary temporary support 15 (e.g.,polyethylene-laminated paper) and a relief mold (e.g., an embossingroll), instead of using the special temporary supports 15 illustrated inFIGS. 3 to 6.

FIGS. 9(a) and 9(b) illustrate the step of preparing a temporarymicrospherical lens-supporting sheet 17 according to a conventionallyknown method and the step of depositing a metal on this sheet 17.Specifically, these steps may be carried out in the same manner asdescribed previously in connection with FIGS. 7(a) and 7(b), exceptthat, as temporary support 15, an ordinary temporary support having noaperture is used in place of the temporary support having aperturesformed by cutting out some parts thereof.

FIG. 9(c) illustrates the step of embedding microspherical lenses in afunctional resin layer 7, which step forms a characteristic feature ofthis method.

A support 11 comprising a laminate of a functional resin layer 7 and areinforcing layer 10 is prepared in the same manner as describedpreviously in connection with FIG. 7(c), and superposed on themetal-coated temporary microspherical lens-supporting sheet 17 preparedas illustrated in FIG. 9(b). In this step, support 11 is superposed ontemporary microspherical lens-supporting sheet 17 in such a way thatfunctional resin layer 7 of support 11 comes into contact with thedeposited metal film (5)-bearing surfaces of microspherical lenses 4projecting above temporary microspherical lens-supporting sheet 17.

Then, using a relief mold 21 (e.g., an embossing roll, mesh roll orgravure roll) disposed on the back side of temporary microsphericallens-supporting sheet 17 [i.e. , on the backing layer (10) side oftemporary microspherical lens-supporting sheet 17 in this FIG. 9(c)],the resulting assembly is heated, if necessary, to soften functionalresin layer 7. At the same time, this assembly is pressed between thisrelief mold 21 and a back-up means (e.g., a rubber roll 22) disposedoppositely on the side of support 11. Thus, the deposited metal film(5)-bearing approximately hemispherical surfaces of microsphericallenses 4 are embedded in functional resin layer 7 to a depth equal toabout 1/6 to 1/2 of the diameter thereof. During this process, themicrospherical lenses embedded in functional resin layer 7 are onlythose present substantially in the parts pressed by relief mold 21, sothat functional resin layer 7 produces regions in which microsphericallenses 4 are embedded and regions in which no microspherical lens isembedded. Accordingly, the raised surface of relief mold 21 used mayhave a shape corresponding to that of the microspherical lens-embeddingregions of the base sheet.

Alternatively, in this step of embedding microspherical lenses in afunctional resin layer 7, relief mold 21 may be disposed on the backside of support 11 (i.e., on the side of PET process film 18), ascontrasted with this FIG. 9(c). That is, the assembly obtained bysuperposing support 11 on temporary microspherical lens-supporting sheet17 may be pressed between this relief roll 21 and back-up means 22disposed oppositely on the backing layer (14) side of temporarymicrospherical lens-supporting sheet 17. Thus, microspherical lenses 4can be embedded only in those parts of functional resin layer 7 whichare pressed by relief mold 21.

Moreover, in this step, the deposited metal film present on temporarymicrospherical lens-supporting sheet 17 between microspherical lenses 4should be prevented from coming into direct contact with the surface offunctional resin layer 7 so that the deposited metal film may not betransferred to the surface of functional resin layer 7. To this end,there may be used any of the specific means described previously inconnection with the step of FIG. 7(c).

FIGS. 9(d) and 9(e) illustrate the temporary support stripping step andthe bond forming step. These steps may be carried out in exactly thesame manner as described previously in connection with FIGS. 7(d) and7(e). Thus, there is obtained lens type functional retroreflectivesheeting in accordance with the present invention.

EXAMPLES

The present invention is more specifically explained with reference tothe following examples. Retroreflectivity, the afterglow brightness andvisibility rating of light-storing luminous retroreflective sheeting,and the ultraviolet-excited luminous brightness and visibility rating ofultraviolet-excited luminous retroreflective sheeting were measured orevaluated according to the following procedures.

(1) Retroreflectivity

Using a MODEL 920 retroreflectivity measuring instrument (manufacturedby Advanced Retro Technology, INC.), the amount of light retroreflectedby a 100 mm×100 mm sample of luminous retroreflective sheeting wasmeasured according to JIS Z9117 at an angle of observation of 0.2° andan angle of incidence of 5°. Measurements were made with respect to fivesuitably chosen points and the measured values were averaged todetermine the retroreflectivity of the sample.

(2) Afterglow Brightness of Light-storing Luminous RetroreflectiveSheeting

After a 100 mm×100 mm sample of light-storing luminous retroreflectivesheeting was allowed to stand in the dark for 12 hours, the sample wasirradiated with a D65 common light source for 30 minutes at anilluminance of 1,000 Ix, and allowed to stand in the dark for 10minutes. Then, using a luminance meter ("LS-100"; manufactured byMinoruta Camera Co., Ltd.), the intensity of afterglow in an about 5 mmΦspot was measured at a distance of about 30 cm from the sample.Measurements were made with respect to five suitably chosen positionsand the afterglow brightness of the light-storing luminousretroreflective sheeting was determined according to the followingequation. ##EQU1## (3) Visibility Rating of Light-storing LuminousRetroreflective Sheeting

A letter "N" was cut out from light-storing luminous retroreflectivesheeting and affixed to a 300 mm×300 mm aluminum plate as a displaysign. On the other hand, the background was formed of encapsulated lensretroreflective sheeting ["Nikka Light ULS F806" (blue); manufactured byNikka Polymer Co., Ltd.]. The specimen so prepared was allowed to standin the dark for 12 hours. Thereafter, the specimen was irradiated with aD65 common light source for 30 minutes at an illuminance of 1,000 Ix,and allowed to stand in the dark for 8 hours. Then, the visibility ofthe specimen was evaluated by 20 male and female persons, aged 18 to 50,at a distance of about 30 m from the specimen. The degree of visibilitywas rated on the following basis, and the visibility rating of thespecimen was expressed by the average value.

5: Very clearly visible.

4: Moderately visible.

3: Barely visible.

2: Vaguely visible (the letter is hardly discernible).

1: Completely invisible.

(4) Ultraviolet-excited Luminous Brightness of Ultraviolet-excitedLuminous Retroreflective Sheeting

An ultraviolet light irradiator comprising four 10W ultravioletlight-emitting fluorescent lamps was provided. On the front side, thisirradiator was fitted with a visible light cut-off filter so as toradiate near ultraviolet light ranging in wavelength from 300 nm to 420nm with a dominant wavelength of about 360 nm. Using this irradiator, a100 mm×100 mm sample was irradiated from above so that the surface ofthe ultraviolet-excited luminous regions received a radiant energy 0.88mW/cm². Then, using a luminance meter ("LS-100"; manufactured byMinoruta Camera Co., Ltd.), the luminous brightness in an about 5 mmΦspot was measured at a distance of about 30 cm right above the sample.Measurements were made with respect to five suitably chosen positionsand the average ultraviolet-excited luminous brightness of theultraviolet-excited luminous retroreflective sheeting was determinedaccording to the following equation. ##EQU2## (5) Visibility Rating ofUltraviolet-excited Luminous Retroreflective Sheeting

Letters were cut out from ultraviolet-excited luminous retroreflectivesheeting and affixed to a 2,200 mm×2,700 mm aluminum plate as a displaysign. On the other hand, the background was formed of encapsulated lensretroreflective sheeting ["Nikka Light ULS F806" (blue); manufactured byNikka Polymer Co., Ltd.]. The information board so made was installed insuch a way that the distance between its lower end and the ground wasabout 4 m and the surface of the board was disposed almost vertically. Afloodlight projector comprising a 400W high-pressure mercury-vapor lampwas installed at a position 5 meters away from the point just below themiddle of the width of the information board in a direction forming anangle of 45° with the surface thereof, and adjusted so that the wholesurface of the information board was irradiated with ultraviolet light.

Then, the visibility of the specimen was evaluated at night by 20 maleand female persons, aged 18 to 50, at a position which was about 50meters away from the point just below the middle of the width of theinformation board in a direction perpendicular to the surface of theinformation board and lay 5 meters rightward facing the informationboard. The degree of visibility was rated on the following basis, andthe visibility rating of the information board was expressed by theaverage value.

5: Very clearly visible.

4: Moderately visible.

3: Barely visible.

2: Vaguely visible (the letters are hardly discernible).

1: Completely invisible.

Example 1

In a temporary support prepared by laminating an about 20 μm thickpolyethylene (PE) layer to paper, a plurality of apertures in the shapeof large and small circles as shown in FIG. 3 were formed by cutting outparts thereof with a rotary die cutter. The total area of the apertureswas about 65% based on the surface area of the temporary support beforecutting out.

The temporary support having apertures formed therein was heated toabout 105° C. Then, glass beads having an average diameter of about 65μm and a refractive index of about 1.91 were scattered thereover in sucha way that they were evenly and densely distributed so as to form amono-layer, and pressed with nip rolls to embed the glass beads in thePE layer to a depth equal to about 1/3 of the diameter thereof.Thereafter, excess glass beads were removed by a spray of air to obtaina temporary glass bead-supporting sheet. Then, according to a vacuumevaporation process, aluminum was deposited on that surface of thetemporary glass bead-supporting sheet on which the glass beads wereexposed. Thus, a vacuum-evaporated film having a thickness of about 0.1μm was formed on the approximately hemispherical surfaces of the glassbeads.

Next, an about 20 μm thick polyethylene terephthalate (PET) process filmwhich had been made releasable by treatment with silicone resin wasprovided, and a mixed solution composed of 100 parts by weight of anacrylic resin solution [a methyl isobutyl ketone (MIBK)/toluene (1/1)solution of an acrylic resin prepared by copolymerizing 20% by weight ofmethyl methacrylate (MMA), 65% by weight of ethyl acrylate (EA) and 15%by weight of 2-hydroxyethyl methacrylate (HEMA) and having a solidcontent of 50% by weight], 21.5 parts by weight of rutile-type titaniumdioxide, and 14.2 parts by weight of a hexamethylene diisocyanate(HMDI)-based crosslinking agent having a solid content of 75% by weight[in the form of a 1-methoxypropyl acetate-2/xylene (1/1) solution] wasapplied onto the aforesaid process film and dried to form a reinforcinglayer having a thickness of about 30 μm.

Thereafter, a light-storing luminous resin composition obtained bymixing 100 parts by weight of an acrylic resin solution different fromthe above-described one [a MIBK/toluene (1/1) solution of an acrylicresin prepared by copolymerizing 40% by weight of MMA, 55% by weight ofEA and 5% by weight of HEMA and having a solid content of 50% by weight]with 120 parts by weight of an inorganic oxide type light-storingpigment ("N-Yako"; manufactured by Nemoto Special Chemicals Co., Ltd.)was applied onto the aforesaid reinforcing layer and dried to form alight-storing luminous resin layer having a thickness of about 250 μm.Thus, there was obtained a support comprising a laminate of areinforcing layer and a light-storing luminous resin layer.

The previously prepared temporary glass bead-supporting sheet wassuperposed on this support in such a way that the metal-coated side ofthe glass beads positioned on the temporary glass bead-supporting sheetfaced the light-storing luminous resin layer surface of the support.This assembly was heated to 85° C. under pressure to embed the glassbeads in the light-storing luminous resin layer of the support to adepth equal to about 1/3 of the diameter thereof. Then, the temporarysupport was stripped from the resulting temporary glass bead-supportingsheet/support laminate to obtain a base sheet having a polka-dottedappearance comprising glass bead-embedding regions in which thedeposited metal film-free approximately hemispherical surfaces of theglass beads were exposed on the surface thereof, and glass bead-freeregions in which no glass bead was embedded. In this base sheet, theareas of the glass bead-embedding regions and the glass bead-freeregions were about 35% and about 65%, respectively, based on the totalarea of the surface on which the glass beads were exposed.

After this base sheet was aged at 35° C. for 14 days to bring thecrosslinking of the reinforcing layer to substantial completion, anabout 50 μm thick acrylic resin film ("Acriprene"; manufactured byMitsubishi Rayon Co., Ltd.) used as a transparent protective film wassuperposed on that surface of the base sheet to which the glass beadshad been transferred. This assembly was passed between a metallicembossing roll having network-like relief with a line width of 1.3 mmand heated to a surface temperature of about 190° C. and a rubber rollheated to a surface temperature of about 60° C., in such a way that thetransparent protective film came into contact with the rubber roll. As aresult, the base sheet was pressed against the metallic embossing rollfrom the side of the PET process film to melt and partially thermoformthe base sheet and thereby bond the base sheet to the transparentprotective sheet. Thus, there was obtained light-storing luminousretroreflective sheeting of the encapsulated lens structure havingretroreflective regions and light-storing luminous regions.

The areas of the retroreflective regions and the light-storing luminousregions in the light-storing luminous retroreflective sheeting thusobtained, and the retroreflectivity, afterglow brightness and visibilitythereof are shown in Table 1 which will be given later. As can be seenfrom these data, this retroreflective sheeting was an excellent producthaving good visibility even at night and meeting the purpose of thepresent invention.

Example 2

A temporary glass bead-supporting sheet was obtained in the same manneras in Example 1, except that an ordinary temporary support prepared bylaminating an about 20 μm thick polyethylene (PE) layer to paper andhaving no apertures formed therein was used in place of the temporarysupport having apertures formed therein. Then, according to a vacuumevaporation process, aluminum was deposited on its surface on which theglass beads were exposed. Thus, a vacuum-evaporated film having athickness of about 0.1 μm was formed on the approximately hemisphericalsurfaces of the glass beads.

On the other hand, using an about 20 μm thick PET process film which hadbeen made releasable, a support comprising a laminate of a reinforcinglayer and a light-storing luminous resin layer was formed in the samemanner as in Example 1.

Next, the previously prepared temporary glass bead-supporting sheet wassuperposed on this support in such a way that the metal-coated side ofthe glass beads positioned on the temporary glass bead-supporting sheetfaced the light-storing luminous resin layer surface of the support.This assembly was passed between a metallic embossing roll havingnetwork-like relief with a line width of 1.3 mm and heated to a surfacetemperature of about 130° C. and a rubber roll heated to a surfacetemperature of about 60° C., in such a way that the temporary glassbead-supporting sheet came into contact with the metallic embossingroll. Thus, only in those parts of the temporary glass bead-supportingsheet which were pressed by the raised pattern of the metallic embossingroll, the glass beads were embedded in the light-storing luminous resinlayer to a depth equal to about 1/3 of the diameter thereof. Thereafter,the procedure of Example 1 was repeated to obtain a base sheet dividedinto glass bead-embedding regions in which the deposited metal film-freeapproximately hemispherical surfaces of the glass beads were exposed onthe surface thereof, and glass bead-free regions in which no glass beadwas embedded. In this base sheet, the areas of the glass bead-embeddingregions and the glass bead-free regions were about 47% and about 53%,respectively, based on the total area of the surface on which the glassbeads were exposed.

After this base sheet was aged at 35° C. for 14 days to bring thecrosslinking of the reinforcing layer to substantial completion, it wasworked up in substantially the same manner as in Example 1. Thus, therewas obtained light-storing luminous retroreflective sheeting of theencapsulated lens structure having retroreflective regions andlight-storing luminous regions.

The areas of the retroreflective regions and the light-storing luminousregions in the light-storing luminous retroreflective sheeting thusobtained, and the retroreflectivity, afterglow brightness and visibilitythereof are shown in Table 1 which will be given later. As can be seenfrom these data, this retroreflective sheeting was an excellent producthaving good visibility even at night and meeting the purpose of thepresent invention.

Example 3

In the step of partially transferring the glass beads as described inExample 2, the assembly was passed between a metallic embossing rollheated to a surface temperature of about 130° C. and a rubber rollheated to a surface temperature of about 60° C. in the same manner as inExample 2, except that the PET process film attached to the support wasbrought into contact with the metallic embossing roll instead ofbringing the temporary glass bead-supporting sheet into contact with themetallic embossing roll. Thus, only in those parts of the light-storingluminous resin layer which were pressed by the raised pattern of themetallic embossing roll, the glass beads were embedded in thelight-storing luminous resin layer to a depth equal to about 1/3 of thediameter thereof. Thereafter, the procedure of Example 1 was repeated toobtain a base sheet divided into glass bead-embedding regions in whichthe deposited metal film-free approximately hemispherical surfaces ofthe glass beads were exposed on the surface thereof, and glass bead-freeregions in which no glass bead was embedded. In this base sheet, theareas of the glass bead-embedding regions and the glass bead-freeregions were about 47% and about 53%, respectively, based on the totalarea of the surface on which the glass beads were exposed.

Thereafter, this base sheet was worked up in substantially the samemanner as in Example 1. Thus, there was obtained light-storing luminousretroreflective sheeting of the encapsulated lens structure havingretroreflective regions and light-storing luminous regions.

The areas of the retroreflective regions and the light-storing luminousregions in the light-storing luminous retroreflective sheeting thusobtained, and the retroreflectivity, afterglow brightness and visibilitythereof are shown in Table 1 which is given below. As can be seen fromthese data, this retroreflective sheeting was an excellent producthaving good visibility even at night and meeting the purpose of thepresent invention.

                  TABLE 1                                                         ______________________________________                                        Light-storing                                                                              Retrore-                                                         luminous     flective                                                                              Retrore-  Afterglow                                      regions      regions flectivity                                                                              brightness                                                                           Visibility                              (%)          (%)     (cd/lx · cm.sup.2)                                                             (mcd/m.sup.2)                                                                        rating                                  ______________________________________                                        Example 1                                                                            77        23       77      91    4                                     Example 2                                                                            67        33      155     160    5                                     Example 3                                                                            67        33      150     140    5                                     ______________________________________                                    

Example 4

In Example 1, instead of the step in which a light-storing luminousresin composition obtained by mixing 100 parts by weight of an acrylicresin solution [containing a copolymer of MMA/EA/HEMA=40/55/5 (% byweight) and having a solid content of 50% by weight] with 120 parts byweight of a light-storing pigment ("N-Yako"; manufactured by NemotoSpecial Chemicals Co., Ltd.) was applied and dried to form alight-storing luminous resin layer having a thickness of about 250 μm, astep was carried out in which an ultraviolet-excited luminous resincomposition obtained by mixing 100 parts by weight of the same acrylicresin solution with 120 parts by weight of an ultraviolet-excitedinorganic oxide type fluorescent pigment ["Aurorainbow A-160" (green);manufactured by Nemoto Special Chemicals Co., Ltd.] was applied anddried to form an ultraviolet-excited luminous resin layer having athickness of about 100 μm. Excepting this, a support comprising alaminate of a reinforcing layer and a green light-emittingultraviolet-excited luminous resin layer was prepared in substantiallythe same manner as in Example 1.

Thereafter, in substantially the same manner as in Example 1, glassbeads were embedded in the ultraviolet-excited luminous resin layer ofthe aforesaid support to obtain a base sheet having a polka-dottedappearance comprising glass bead-embedding regions in which thedeposited metal film-free approximately hemispherical surfaces of theglass beads were exposed on the surface thereof, and glass bead-freeregions in which no glass bead was embedded. In this base sheet, theareas of the glass bead-embedding regions and the glass bead-freeregions were about 35% and about 65%, respectively, based on the totalarea of the surface on which the glass beads were exposed. After thisbase sheet was aged at room temperature for 20 days to bring thecrosslinking of the reinforcing layer to substantial completion, it wasworked up in substantially the same manner as in Example 1. Thus, therewas obtained ultraviolet-excited luminous retroreflective sheeting ofthe encapsulated lens structure having retroreflective regions andultraviolet-excited (green) luminous regions.

The areas of the retroreflective regions and the ultraviolet-excitedluminous regions in the ultraviolet-excited luminous retroreflectivesheeting thus obtained, and the retroreflectivity, ultraviolet-excitedluminous brightness and visibility thereof are shown in Table 2 whichwill be given later. As can be seen from these data, thisretroreflective sheeting was an excellent product having good visibilityeven at night and meeting the purpose of the present invention.

Example 5

A support comprising a laminate of a reinforcing layer and a redlight-emitting ultraviolet-excited luminous resin layer was prepared inthe same manner as in Example 4, except that 120 parts by weight of ared light-emitting inorganic fluorescent pigment ["A-120"; manufacturedby Nemoto Special Chemicals Co., Ltd.] was used in place of 120 parts byweight of the ultraviolet-excited inorganic oxide type fluorescentpigment ["Aurorainbow A-160" (green); manufactured by Nemoto SpecialChemicals Co., Ltd.].

Thereafter, the procedure of Example 4 was repeated to obtain a basesheet having a polka-dotted appearance comprising glass bead-embeddingregions in which the deposited metal film-free approximatelyhemispherical surfaces of the glass beads were exposed on the surfacethereof, and glass bead-free regions in which no glass bead wasembedded. In this base sheet, the areas of the glass bead-embeddingregions and the glass bead-free regions were about 35% and about 65%,respectively, based on the total area of the surface on which the glassbeads were exposed. After this base sheet was aged at room temperaturefor 20 days to bring the crosslinking of the reinforcing layer tosubstantial completion, it was worked up in the same manner as inExample 4. Thus, there was obtained ultraviolet-excited luminousretroreflective sheeting of the encapsulated lens structure havingretroreflective regions and ultraviolet-excited (red) luminous regions.

The areas of the retroreflective regions and the ultraviolet-excitedluminous regions in the ultraviolet-excited luminous retroreflectivesheeting thus obtained, and the retroreflectivity, ultraviolet-excitedluminous brightness and visibility thereof are shown in Table 2 whichwill be given later. As can be seen from these data, thisretroreflective sheeting was an excellent product having good visibilityeven at night and meeting the purpose of the present invention.

Example 6

Using a rotary screen, an acrylic resin solution [containing a copolymerof MMA/EA=34/66 (% by weight) and having a solid content of 50% byweight] was printed on kraft paper having a basis weight of 78 g/m² soas to form square patterns as shown in FIG. 5. Thus, there was obtaineda temporary support on which a glass bead-embedding resin layer having adry thickness of about 20 μm was formed. The total area of the parts inwhich the glass bead-embedding resin layer was formed was about 50%based on the surface area of the temporary support.

The temporary support thus obtained was heated to about 100° C. Then,glass beads similar to those used in Example 1 were scattered thereoverin such a way that they were evenly and densely distributed so as toform a mono-layer, and pressed with nip rolls to embed the glass beadsin the glass bead-embedding resing layer (the acrylic resin layer) to adepth equal to about 1/3 of the diameter thereof. Thereafter, excessglass beads were removed by a spray of air to obtain a temporary glassbead-supporting sheet. Then, according to a vacuum evaporation process,aluminum was deposited on that surface of the temporary glassbead-supporting sheet on which the glass beads were exposed. Thus, avacuum-evaporated film having a thickness of about 0.1 μm was formed onthe approximately hemispherical surfaces of the glass beads.

Then, a support comprising a laminate of a reinforcing layer and a greenlight-emitting ultraviolet-excited luminous resin layer was prepared inthe same manner as in Example 4. Thereafter, the procedure of Example 4was repeated to obtain a base sheet comprising square glassbead-embedding regions in which the deposited metal film-freeapproximately hemispherical surfaces of the glass beads were exposed onthe surface thereof, and glass bead-free regions in which no glass beadwas embedded. In this base sheet, the areas of the glass bead-embeddingregions and the glass bead-free regions were about 50% and about 50%,respectively, based on the total area of the surface on which the glassbeads were exposed. After this base sheet was aged at room temperaturefor 20 days to bring the cross linking of the reinforcing layer tosubstantial completion, it was worked up in substantially the samemanner as in Example 4. Thus, there was obtained ultraviolet-excitedluminous retroreflective sheeting of the encapsulated lens structurehaving retroreflective regions and ultraviolet-excited (green) luminousregions.

The areas of the retroreflective regions and the ultraviolet-excitedluminous regions in the ultraviolet-excited luminous retroreflectivesheeting thus obtained, and the retroreflectivity, ultraviolet-excitedluminous brightness and visibility thereof are shown in Table 2. As canbe seen from these data, this retroreflective sheeting was an excellentproduct having good visibility even at night and meeting the purpose ofthe present invention.

Example 7

In Example 2, a support comprising a laminate of a reinforcing layer anda green light-emitting ultraviolet-excited luminous resin layer wasprepared in the same manner as in Example 4, instead of preparing asupport comprising a laminate of a reinforcing layer and a light-storingluminous resin layer. Thereafter, in substantially the same manner as inExample 2, glass beads were embedded in the ultraviolet-excited luminousresin layer of the aforesaid support to obtain a base sheet divided intoglass bead-embedding regions in which the deposited metal film-freeapproximately hemispherical surfaces of the glass beads are exposed onthe surface thereof, and glass bead-free regions in which no glass beadwas embedded. In this base sheet, the areas of the glass bead-embeddingregions and the glass bead-free regions were about 47% and about 53%,respectively, based on the total area of the surface on which the glassbeads were exposed. After this base sheet was aged at 35° C. for 14 daysto bring the crosslinking of the reinforcing layer to substantialcompletion, it was worked up in substantially the same manner as inExample 1. Thus, there was obtained ultraviolet-excited luminousretroreflective sheeting of the encapsulated lens structure havingretroreflective regions and ultraviolet-excited (green) luminousregions.

The areas of the retroreflective regions and the ultraviolet-excitedluminous regions in the ultraviolet-excited luminous retroreflectivesheeting thus obtained, and the retroreflectivity, ultraviolet-excitedluminous brightness and visibility thereof are shown in Table 2 whichwill be given later. As can be seen from these data, thisretroreflective sheeting was an excellent product having good visibilityeven at night and meeting the purpose of the present invention.

Example 8

In Example 7, a support comprising a laminate of a reinforcing layer anda red light-emitting ultraviolet-excited luminous resin layer wasprepared in the same manner as in Example 5, instead of preparing asupport comprising a laminate of a reinforcing layer and a greenlight-emitting ultraviolet-excited luminous resin layer. Thereafter, theprocedure of Example 5 was repeated to obtain a base sheet divided intoglass bead-embedding regions in which the deposited metal film-freeapproximately hemispherical surfaces of the glass beads are exposed onthe surface thereof, and glass bead-free regions in which no glass beadwas embedded. In this base sheet, the areas of the glass bead-embeddingregions and the glass bead-free regions were about 47% and about 53%,respectively, based on the total area of the surface on which the glassbeads were exposed. After this base sheet was aged at 35° C. for 14 daysto bring the crosslinking of the reinforcing layer to substantialcompletion, it was worked up in substantially the same manner as inExample 1. Thus, there was obtained ultraviolet-excited luminousretroreflective sheeting of the encapsulated lens structure havingretroreflective regions and ultraviolet-excited (red) luminous regions.

The areas of the retroreflective regions and the ultraviolet-excitedluminous regions in the ultraviolet-excited luminous retroreflectivesheeting thus obtained, and the retroreflectivity, ultraviolet-excitedluminous brightness and visibility thereof are shown in Table 2 whichwill be given later. As can be seen from these data, thisretroreflective sheeting was an excellent product having good visibilityeven at night and meeting the purpose of the present invention.

                  TABLE 2                                                         ______________________________________                                                                       Ultraviolet-                                   Ultraviolet- Retrore-          excited                                        excited lumi-                                                                              flective                                                                              Retrore-  luminous                                                                              Visi-                                  nous regions regions flectivity                                                                              brightness                                                                            bility                                 (%)          (%)     (cd/lx · cm.sup.2)                                                             (cd/m.sup.2)                                                                          rating                                 ______________________________________                                        Example 4                                                                            76        24      80      271     5                                    Example 5                                                                            77        23      82       69     5                                    Example 6                                                                            67        33      111     235     5                                    Example 7                                                                            67        33      150     192     5                                    Example 8                                                                            67        33      148      48     5                                    ______________________________________                                    

EFFECTS OF THE INVENTION

As described above, the lens type functional retroreflective sheeting ofthe present invention not only reflects light (e.g., sunlight) in thedaytime and exhibit good visibility, but also functions at night in sucha way that its retroreflective regions reflect light from a light source(e.g., automobile headlamps) back toward the light source and therebyafford good visibility to viewers positioned in the direction of thelight source (e.g., automobile drivers). Moreover, where the visualfunctionality presenting regions are light-storing luminous regions,these regions store sunlight in the daytime and light radiating fromfluorescent lamps, automobile headlamps or the like at night, emit lightgradually even in the dark in which there is no light source, andthereby afford good luminosity or night visibility to drivers,pedestrians and the like.

Furthermore, where the visual functionality presenting regions areultraviolet-excited luminous regions, these regions emit light uponexposure to ultraviolet light, and thereby afford good visibility atnight to viewers positioned in directions different from the that of thelight source.

We claim:
 1. Lens type functional retroreflective sheeting havingretroreflective regions and non-retroreflective luminous visual regionscomprising:a base sheet comprising a support comprisinga functionalresin layer comprising a resin component and at least one functionallight emitting pigment having light-storing or fluorescent properties,microspherical lens-embedding regions in which microspherical lenseswith a deposited metal film coating the approximately hemisphericalsurfaces thereof are densely distributed on the surface of thefunctional resin layer of the support so as to form substantially amono-layer, their approximately hemispherical surfaces coated with thedeposited metal film are embedded in the functional resin layer, andtheir approximately hemispherical surfaces not coated with the depositedmetal film are exposed on the functional resin layer, and microsphericallens-free regions in which substantially no microspherical lens isembedded and the functional resin layer is exposed; a transparentprotective film disposed above that surface of said base sheet on whichmicrospherical lenses are exposed; and bonds at which said base sheetand said transparent protective film are partly bonded together so as tohold a layer of air between the layer of microspherical lenses and saidtransparent protective film, said retroreflective sheeting havingretroreflective regions comprising those parts of the microsphericallens-embedding regions in which said bonds are not formed, and visualfunctionality presenting regions comprising at least the microsphericallens-free regions.
 2. Lens type functional retroreflective sheeting asclaimed in claim 1 wherein said bonds are in the form of continuouslines and, in cooperation with said base sheet and said transparentprotective film, define a large number of hermetically sealedmicrocells.
 3. Lens type functional retroreflective sheeting as claimedin claim 1 wherein said bonds have been formed by partiallythermoforming the functional resin layer.
 4. Lens type functionalretroreflective sheeting as claimed in claim 1 wherein the proportionsof the area of said retroreflective regions and the area of said visualfunctionality presenting regions are 10 to 60% and 40 to 90%,respectively, based on the total area of the light incidence sidesurface of said retroreflective sheeting.
 5. Lens type functionalretroreflective sheeting as claimed in claim 1 wherein the functionalpigment is at least one light-storing pigment, the functional resinlayer is a light-storing luminous resin layer, and said visualfunctionality presenting regions are light-storing luminous regions. 6.Lens type functional retroreflective sheeting as claimed in claim 5wherein the light-storing pigment comprises an oxide type light-storingpigment.
 7. Lens type functional retroreflective sheeting as claimed inclaim 6 wherein the light-storing pigment is an oxide type light-storingpigment comprising matrix crystals of a metal oxide of the generalformula MAl₂ O₄ (in which M represents at least one alkaline earthmetal) containing rare earth metal atoms as an activator in an atomicfraction of 1×10⁻⁶ to 0.2 based on the total number of alkaline earthmetal (M) atoms and rare earth metal atoms.
 8. Lens type functionalretroreflective sheeting as claimed in claim 7 wherein the alkalineearth metal is at least one metal selected from the group consisting ofCa, Ba and Sr.
 9. Lens type functional retroreflective sheeting asclaimed in claim 7 wherein the rare earth metal is at least one metalselected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd,Tb, Dy, Ho, Er, Tm, Yb and Lu.
 10. Lens type functional retroreflectivesheeting as claimed in claim 7 wherein, the light-storing pigmentfurther contains a coactivator comprising at least one metal selectedfrom the group consisting of Mn, Sn and Bi, in an atomic fraction of1×10⁻⁶ to 0.2 based on the total number of alkaline earth metal (M)atoms, rare earth metal atoms and coactivator metal atoms.
 11. Lens typefunctional retroreflective sheeting as claimed in claim 5 wherein thelight-storing luminous resin layer contains the light-storing pigment inan amount of 100 to 900 parts by weight per 100 parts by weight of theresin component.
 12. Lens type functional retroreflective sheeting asclaimed in claim 5 wherein the light-storing pigment has an afterglowcharacteristic of not less than 150 mcd/m².
 13. Lens type functionalretroreflective sheeting as claimed in claim 5 wherein the light-storingpigment has an afterglow characteristic of not less than 250 mcd/m². 14.Lens type functional retroreflective sheeting as claimed in claim 1wherein the functional pigment comprises an ultraviolet-excitedfluorescent pigment, the functional resin layer is anultraviolet-excited luminous resin layer, and said visual functionalitypresenting regions are ultraviolet-excited luminous regions.
 15. Lenstype functional retroreflective sheeting as claimed in claim 14 whereinthe ultraviolet-excited fluorescent pigment is at least one inorganicfluorescent pigment.
 16. Lens type functional retroreflective sheetingas claimed in claim 15 wherein the ultraviolet-excited fluorescentpigment is an inorganic fluorescent pigment containing at least onemember selected from the group consisting of red light-emittinginorganic fluorescent pigments, green light -emitting inorganicfluorescent pigments and blue light-emitting inorganic fluorescentpigments.
 17. Lens type functional retroreflective sheeting as claimedin claim 15 or 16 wherein the inorganic fluorescent pigment has aparticle diameter distribution containing 80% by weight or more ofparticles having a diameter of not greater than 25 μm.
 18. Lens typefunctional retroreflective sheeting as claimed in claim 14 wherein theultraviolet-excited fluorescent pigment emits light upon irradiationwith ultraviolet radiation having a wavelength in the range of 250 to400 nm.
 19. Lens type functional retroreflective sheeting as claimed inclaim 14 wherein the ultraviolet-excited luminous resin layer containsthe ultraviolet-excited fluorescent pigment in an amount of 10 to 600parts by weight per 100 parts by weight of the resin component.
 20. Lenstype functional retroreflective sheeting as claimed in claim 1, 11 or 19wherein the resin component contains, as principal constituent, at leastone resin selected from the group consisting of acrylic resins,polyurethane resins, polyester resins, vinyl chloride resins andfluororesins.
 21. A method of producing lens type functionalretroreflective sheeting which comprises:(a) providing a temporarysupport having been subjected to a treatment for preventingmicrospherical lenses from being temporarily embedded in some partsthereof, supporting a large number of microspherical lenses on thoseparts of said temporary support which allow microspherical lenses to betemporarily embedded, in such a way that the microspherical lenses aredensely distributed so as to form substantially a mono-layer and theapproximately hemispherical surfaces thereof are embedded in saidtemporary support, and thereby preparing a temporary microsphericallens-supporting sheet comprising said temporary support having themicrospherical lenses embedded in some parts thereof; (b) depositing ametal on the microspherical lens-bearing surface of said temporarymicrospherical lens-supporting sheet to form a deposited metal film onthose approximately hemispherical surfaces of the microspherical lenseswhich project above said temporary support; (c) separately preparing asupport having a functional resin layer comprising resin component andfunctional pigment having light-storing or fluorescent properties,forming an assembly by superposing said support on said temporarymicrospherical lens-supporting sheet in such a way that the functionalresin layer side of said support comes into contact with themicrospherical lens surfaces projecting above said temporarymicrospherical lens-supporting sheet and having thereon the depositedmetal film, and pressing and laminating the resulting assembly to embedthe deposited metal film-bearing approximately hemispherical surfaces ofthe microspherical lenses in the functional resin layer of said support;(d) stripping said temporary support from the resulting laminate totransfer the microspherical lenses to the functional resin layer of saidsupport; and (e) superposing a transparent protective film on theresulting base sheet having the microspherical lenses embedded in thefunctional resin layer, in such a way that the transparent protectivefilm rests on those deposited metal film-free approximatelyhemispherical surfaces of the microspherical lenses which project abovesaid base sheet, and using a relief mold disposed on the back side ofsaid base sheet to partially thermoform the functional resin layer ofsaid base sheet by the application of heat and pressure and thereby formbonds for bonding the transparent protective film partly to said basesheet.
 22. A method of producing lens type functional retroreflectivesheeting as claimed in claim 21 wherein said temporary support havingbeen subjected to a treatment for preventing microspherical lenses frombeing temporarily embedded in some parts thereof is a temporary supporthaving apertures formed by cutting out some parts thereof.
 23. A methodof producing lens type functional retroreflective sheeting as claimed inclaim 22 wherein the total area of the apertures comprises 30 to 70% ofthe surface area of said temporary support before some parts thereof arecut out.
 24. A method of producing lens type functional retroreflectivesheeting as claimed in claim 21 wherein said temporary support havingbeen subjected to a treatment for preventing microspherical lenses frombeing temporarily embedded in some parts thereof is a temporary supporthaving a temporary microspherical lens-embedding resin layer formed insome parts thereof.
 25. A method of producing lens type functionalretroreflective sheeting as claimed in claim 24 wherein the total areaof the parts on which the temporary microspherical lens-embedding resinlayer is formed comprises 10 to 70% of the surface area of saidtemporary support.
 26. A method of producing lens type functionalretroreflective sheeting as claimed in claim 21 wherein the functionalpigment is a light-storing pigment or an ultraviolet-excited fluorescentpigment.
 27. A method of producing lens type functional retroreflectivesheeting as claimed in claim 26 wherein the functional pigment is thelight-storing pigment which is at least one oxide type light-storingpigment.
 28. A method of producing lens type functional retroreflectivesheeting as claimed in claim 26 wherein the functional pigment is theultraviolet-excited fluorescent which is an inorganic fluorescentpigment containing at least one member selected from the groupconsisting of red light-emitting inorganic fluorescent pigments, greenlight-emitting inorganic fluorescent pigments and blue light-emittinginorganic fluorescent pigments.
 29. A method of producing lens typefunctional retroreflective sheeting which comprises:(a) supporting alarge number of microspherical lenses on a temporary microsphericallens-embedding resin layer formed on some parts of a temporary support,in such a way that the microspherical lenses are densely distributed soas to form substantially a mono-layer and the approximatelyhemispherical surfaces thereof are embedded in the temporarymicrospherical lens-embedding resin layer, and thereby preparing atemporary microspherical lens-supporting sheet comprising said temporarysupport having the microspherical lenses embedded therein; (b)depositing a metal on the microspherical lens-bearing surface of saidtemporary microspherical lens-supporting sheet to form a deposited metalfilm on those approximately hemispherical surfaces of the microsphericallenses which project above said temporary support; (c) separatelypreparing a support having a functional resin layer comprising a resincomponent and functional pigment having light-storing or fluorescentproperties, superposing said support on said temporary microsphericallens-supporting sheet in such a way that the functional resin layer sideof said support comes into contact with the microspherical lens surfacesprojecting above said temporary microspherical lens-supporting sheet andhaving the deposited metal film, and pressing the resulting assembly bymeans of a relief mold disposed on the back side of said temporarymicrospherical lens-supporting sheet or said support to embed thedeposited metal film-bearing approximately hemispherical surfaces of themicrospherical lenses in the functional resin layer of said support; (d)stripping said temporary support from the resulting laminate to transferthe microspherical lenses present in the parts pressed by the reliefmold to the functional resin layer of said support; and (e) superposinga transparent protective film on the resulting base sheet having themicrospherical lenses embedded in the functional resin layer, in such away that the transparent protective film rests on those deposited metalfilm-free approximately hemispherical surfaces of the microsphericallenses which project above said base sheet, and using a relief molddisposed on the back side of said base sheet to partially thermoform thefunctional resin layer of said base sheet by the application of heat andpressure and thereby form bonds for bonding the transparent protectivefilm partly to said base sheet.
 30. A method of producing lens typefunctional retroreflective sheeting as claimed in claim 29 wherein therelief mold used in step (c) is an embossing roll, mesh roll or gravureroll.